#include <bits/stdc++.h>
using namespace std;
// sqrt
int main()
{
    double x;
    cin >> x;
    double l = 0, r = x;
    while(r - l > 1e-2)
    {
        double mid = (l + r) / 2;
        if(mid * mid >= x) r = mid;
        else l = mid; 
    }
    printf("%lf\n", l);
    return 0;
}